Question

Lung Cancer & Smoking Case Study

A causal relationship between cigarette smoking

and lung cancer was first suspected in the 1920s on the basis of clinical observations. To test this apparent association, numerous epidemiologic studies were undertaken between 1930 and

1960. Two studies were conducted by Richard

Doll and Austin Bradford Hill in Great Britain.

The first was a case-control study begun in 1947 comparing the smoking habits of lung cancer patients with the smoking habits of other patients. The second was a cohort study begun in 1951 recording causes of death among British

physicians in relation to smoking habits. This

case study deals first with the case-control study, then with the cohort study.

Data for the case-control study were obtained from hospitalized patients in London and vicinity

over a 4-year period (April 1948 - February

1952). Initially, 20 hospitals, and later more, were asked to notify the investigators of all patients admitted with a new diagnosis of lung cancer. These patients were then interviewed concerning smoking habits, as were controls selected from patients with other disorders

(primarily non-malignant) who were hospitalized in the same hospitals at the same time.

Data for the cohort study were obtained from the population of all physicians listed in the British Medical Register who resided in England and Wales as of October 1951. Information about present and past smoking habits was obtained

by questionnaire. Information about lung cancer came from death certificates and other mortality data recorded during ensuing years.

6: Do you believe the hospitalized persons with lung cancer (cases) are representative (similar) of all patients with lung cancer? Explain your answer.

7:Do you believe the hospitalized persons without lung cancer (controls) are representative (similar) to people in the general population? Explain your answer.

8: : How may these representativeness issues affect interpretation of the study's results? Please discuss how it could affect the odds ratio results for this case-control study.

Answer 1

6. ANS: Hospitalized patients could be the typical representative of the total population considering that individuals are suffering from lung cancer at an advanced stage and undergoing comprehensive treatment, or in some cases nearing death. However, hospitalized lung cancer patients do not accurately equate all lung cancer cases that exist in the given community.

7. ANS: This description could be even lesser for lung cancer patients that are not hospitalized at this time. With an extensive number of medical diagnosis and other health concerns in which individuals consult a health care provider. It may still not be the accurate representation of the total population. However, if there will be an increased in the number of individuals hospitalized for some other health problems aside from lung cancer, that might be an indication for epidemiologists to investigate what triggers the illness which could be social factors or it can be an environmental factor as well.

8. ANS: This representativeness issues may affect the investigation overall result due to selection bias. The primary goal of "control" in a case-control study is to determine the prevalence of exposure of the population of interest from which the cases are being examined. Controls that has been hospitalized for other smoking related health issues that could result in much higher prevalence of smoking in the overall population. The possible outcome of having higher prevalence in a control group is that the risk ratio of lung cancer in this group may be underestimated. Risk ratio may result in a lower degree than the actual estimate.